State of the art magnetic disk drive frames generally are castings or plates on which spindle and actuator assemblies are cantilever mounted. A variation of this approach is the addition of a second L-shaped or C-shaped member for providing support to the other end of the actuator or spindle shaft. Yet another version is a `cake pan` style casting into which the spindle and actuator assemblies are mounted. A thin sheet metal part closes the end of the cake pan while providing support for the opposite ends of the spindle and actuator shafts. A planar board of associated electronics is mounted to the user frame underlying the head-disk assembly and using the full length and width dimensions of the device to complete the electro/mechanical file assembly.
To achieve the maximum storage capability of a magnetic disk data storage device, the areal density of data written on the data surface is maximized by using the highest possible track density and the greatest bit density within each track. The real objective is to obtain the maximum volumetric density within the device which requires that the available space contain the maximum number of storage disks in addition to optimum areal density. Disk drive dimensions are normally limited by a form factor or an industry standard set of length, width and height dimensions. This is a rigid standard that is often more the result of accident than design. The standard is usually the result of a progression of events starting with a flexible disk drive, that sets the standard or in accordance with which using systems provide space in their designs. Rigid disk drives have usually been adapted to replace a flexible disk drive in the same space and have therefore been required to meet the same or standard dimensions in order to obtain acceptance from the users of such storage devices. Drives incorporating 31/2 inch disks have a form factor that is 5.75 inches long, 4 inches wide and 1.625 inches high.
Disk storage devices are particularly susceptible problems arising from uneven clamping or securing forces. In most environments, securing parts at multiple locations avoids problems. However, in a device such as a disk drive, microinch differences cause performance problems infrequently experienced elsewhere. For example, clamping disks on a spindle using a symmetrical pattern of 5 or 6 bolts with a rigid clamping member usually results in localized stress art each bolt location that results in a small localized displacement of the disks at each clamping site. Even minuscule displacements of this nature must be addressed by the track follow technique to avoid error propagation. Similar problems are encountered when a drawn sheet metal cover is clamped or bolted to a base casting on which the head-disk assembly is supported. Small, but meaningful localized displacement of what appears to be a rigid frame must be accommodated to achieve error free write and read operations.